Method of manufacturing filaments



' Jan. 3, 1939. w. p. ZABEL v 2,142,865

METHOD OF MANUFACTURING FILAMENTS Filed Marbh 24, 1957 Figl.

/ F/L AME/v7" WIRE 8r CO/LING OPERATION MANDRE'L HE) T TREA TME/VT a 2CO/L/NG OPERA r/o/v F/LAMENT SEVERED A/VD vJECO/VDARY MANDREL W/ THDRAW/V r ///,,M,,/,,,,?, I

HEAT TREATMENT Fig. 7.

OPERATED MN:

I Inventor: LAMP William P. Zabel,

His A torney.

raw & M9 9 7 incandescentlamps and?moreparticularly to a "mentspreferably of the'double (coiled coil) and.

the triple" (coiled. coiled-coil) helical 'type.-

nn z'rnon on MANUFACTURING V I. WilliamPQZabel, Cleveland Heights,flhiog-assignv a v or toGeneral Electric Company, acorporation of NewYork f Applicant March 24, 1937,.Serial No. 132,763

'ff'soaims. (01. 175-40) invention relates to filamentsfor electricprocess of forming and treating multiple coil fila- One of the-objectsof mylnve'ntion is to produce double and triple helical-filaments ofgreater uxii- 'formityw Heretofore; the filaments varied some- 1 what inlength and '-'were' often' distorted; 'In both cases the direct cause ofthedefectcould not be t'ra'ced -to any particular -part-of the manufac-"turing processflargely because the'defect was likely to' appear --in'an'yof theimanufacturing steps or even'after thefil'ament-was operatedin a lampi 'The defects wer'e believed-=to-be-princi- --pally theresultofchangescausedby the relieving of internal strains within the filament,which were produced therein by the particular coiling method used andwere -not properly relieved :by

the-haflt'reatment: In some cases the coiling operation alone' causedimmediate distortion of the filament coils. My process obviatesthesedisadvantages by providing a more satisfactory coiling "methodandalsoaheat treating method for relieving the strains produced in thewire by the saidcoiling method.

Conventional coiling methods heretofore employed have usually consistedin coiling the filament wire on a mandrel of sufficient length to bespooled, coiling the mandrel and filament coiled thereon about a secondmandrel and, 'if the filament was to be of triple helical form, coilingboth mandrels and twice coiled filament thereon about a third mandrel.With this method even the twice or thrice coiled filament wire, as thecase may be, was coiled in a considerable length which was heat treatedand then severed-with all mandrels remaining in the filament coils. Themandrels 'were finally removed by dissolving in an acid.

The conventional method of coiling is objectionable because of thelength of the coiling operation since local strains are produced in thefilament ;by variations in the coiling tension which gradually build upuntil relieved by the twisting of both the filament and the mandrel.Such strains and twists appear to be inherent in this method ofoperation and do not seriously affect .filament qualityvexcept in thefinal (second or third) coiling operations where the distortion is ofgreater magnitude,

Conventional heat reating consists in passing the filament and mandrelcombination through a furnace at a speed which provides the desiredtreatment and may also consist of other treatpossible before.

ments, in which len'gths-of-said -iilament"'and mandrel combinationequivalent to"several filaments (ten for instance) 'are placed in -aboat in a furnace for the desired length of -time. In

such treatmen'ts-themandrels must -be left in 5 the coils of the.filament wiretokeep-themin position andtherefore must be-considered inthe heat treatment. -,The final-mandrel in multiple -..:coil filamentsis of considerable sizeandi because of its mass and position withinair-irregular filal0 ment; is; effective in ch'angingthe' rate and uni--formity of heatingezand'tcooling. The final man r drel. is.a.lsoof-adifierentmaterial thanthe fllament and is apt to contaminatessaidfilament ment is impractical because of the larger'amount of unwindingand distortion takingpla'ce: =I'hese heat treatments take ,a relativelylong time in comparison ,to my method and,- when :the' fila- '20 mentsare piled one on the othenarie'objectionable because of the pressure-andrestrainin 'eifect of the-filaments .on each other." w

.My process on theother hand is particularly well suited to produce morestable and uniform 25 filaments and permits manufacture of filamentshaving more desirably shaped end sections than The uniformity appears asan increase in consistency in the number of coils and the length of wireturn by turn (1. e. equal weight) 30 of the filaments..

According to my invention the filament wire, which is preferably of theso-called non-sag variety, is first coiled about a comparatively longmandrel preferably at a uniform pitch and, 35 if the filament is to beof the triple helical type,

- is again coiled with the mandrel about a second mandrel. Both theseoperations are performed in the usual manner and result in the filamentwire taking a given shape and developing strains 40 and a tendency tostraighten out an appreciable amount. Accordingly the filament andmandrel assembly are heat treated in-the conventional way to remove aconsiderable portion of the .said strains and the tendency to unwind.From this 45 mandrel and filament coil assembly individual coiled-coilor triple coiled filaments are made one after another successively. Theoperations in the manufacture of coiled coil filaments are, first, tolay a portion of the mandrel and filament coil 50 assembly parallel to asecond temporary mandrel, to coil a succeeding portion of said assemblyabout said temporary mandrel at a given pitch, to draw out a stillfurther succeeding portion of said assembly beyond the end of thetemporary --.porary mandrel; -In--the.-= mamifacture. oftriplecoiledfilaments. the operations are the same ex-.'

Wil'afidliiihh'the first and second manis thenjhe mandrel. Theend-portions of I, --;tlie;filanientsf;iorm legs which'lie parallel tothe 0' axis ,of'jthe filament and which are therefore well 1' coiled onwthetemporary mandrel which adapted to be attached to the leading inwires K of alamp. This shape of leg produced by theconventional methods90f manufacture. The limited time of the coiling -operation .pre-. ventscoiling strains from building upto a'point where they are detrimentaland allows the recoilto loosen the whole filament cell on the'mandrelmandrel, to sever ,thesecond' straight portion now subiected toa heattreatment, as shown in ept'that an.asscmb1Y.-including the twice cniled'I 'pi' the original drawn mandrel and original drawn- Fi'g. 3;} designedto remove a considerable portion filament wire strains aswell as latercoiling strains therein and to partially clean it. The treatment ispreferably divided into two sections, the first being for ab out twelveseconds when the mandrel andthfilainenhwire assembly i2 is [passed,throug h'la furnace l3 containing wet or humidified hydrogen**a'hdretained at 14o0 0., and the 'secondfbeingffor; about sixteen secondswhen said assembly 12 is passed through a second r furnace?-'cjontaining substantially dry (dehy- -dnite cv hydrogen and retainedat 1500" to 1700" so that it can be withdrawn; 'The recoil .is aiIect-.I

ed by physical characteristics of the mandrel'used in the first coil andalso alterationof these characteristics in subsequent heat treatmentofboth the filament coil and mandrel assembly. *The individual filamentsare then heat.treated to cause them to be set in the coiled coil ortriple coiled form whereupon the .other fixed mandrels are removed,preferably by dissolving in 'acid. The

filaments are then mounted on the leading-in.

C. "Ifhe'furn'aceHIS illustrated is provided with an' electricaljheatingelement It. In the first section of the treatment, the moisture in thehydrogen combineswlth the graphite-of the coating to partially clean thefilament wire and mandrel be theoperations including thefirst heattneat--ment, the winding of the mandrel and filament wire assemblyon the:final (temporary!- mandrel and the removal of saidfinal ortemporarymantreatment)-- is done r i mandreliiisthethird mandrel whentriple coiled drelbefore further work (heat on the filamentwire.

v The advantages of my process of manufacture will be more readilyunderstood fromtthe detailed description which follows of one specificappli' cation of my process and from the drawing. The drawingillustrates diagrammatically in Figs. 1 to! inclusivethe various stepsin the process of my invention. r

Patent 1,410,499 of March 21, 1922. Uncleaned wire is that stillretaining the coating formed by the graphite, etc., lubricant used inthe drawing process. Because of the lubricating value of'the coatingincoiling the wire, and the expense of removing it, said coating ispreferably left ereon.. The filament wire I0 is coiled about a wiremandrel H as shown in Fig. 2, said mandrel ll being four mils indiameter and of sufiicient length to be conveniently spooled. Thefilament wire 10 in thisinstanoe is coiled at a pitch of 335 turns perinch on a mandrel l I which is preferably made of molybdenum or someother material of which 7.: the filament wire and mandrel assembly areagain To show specifically all features of or the uncleanedv'arietm Ifnon-sag, the-wire. i0 is preferably made according to the Peer:-

as well as removes a portion of the strains. the secondsection of thetreatment the heat re moves a considerable portion of the strains in"the filament assembly" l2. Both-sections of. the treatment are notalways required in which case cnly;the second section thereof is used.This is particularly true-when the cleaned filament wire .Ilis usedalthough for the uncleanedwire wet "hydrogen --is"*preferred. Dryhydrogen can be used :in both-heat treatments if desired.

; .-After the heat treatment :the mandrel and filame'nt wire-assembly I2is coiled .on a-second tem- -p rary-mandrel is, as shown in Fig. 4. Thisfilaments are-being formed. The operation is preferably performed by amachine of the type shown in Illingworth Patent No. 1,771,927 of July29, 1930, and is an intermittent-' -oparation interrupted-atintervalswhile straight end portions of-the filament are produced and while thecompletedfilament is severed from the-remainder. As shown, one end ofthe mandrel and filament wire assembly i2 is first gripped between thejaws "Sand I1 whereupon the spindle l8 carrying the mandrel and filamentwire-assembly i2 is rotated about the axis of the second mandrel l5 assaid mandrel l5 and jaws l6 and I1 are moved at the desired rate awayfrom the spindle iii. The mandrel, and filament wire assembly l2 passesthrough an off-center hole in the spindle l8 and is wound around thetemporary mandrel I5 by -the rotation of said spindle l8. The movementof -tliemandrel l5 and the jaws IG'and ll away from the spiiidle Itcauses the windings to be advanced along the mafidrel l5. In thisinstance the jaws i6 and I1 hold 168 mils (4 mm.) of the mandrel andfilament wire assembly l2, and the mandrel I5 is approximately 15.3 milsin diameter. The coiling 'is done at a pitch of 76 turns per inch butonlygil. turns. are placed on the mandrel l before the end of themandrel is reached and rotation of the spindle I8 is stopped. A straightsection l9 (Fig. 5) substantially the equivalent of two of the 168 milend portions is now drawn out whereupon all motion stops.

An individual coiled coil filament in the .instance illustrated is nowcompletely formed and, as shown in Fig. 5, the straight portion I9 issevered by the knives 20 and 2|. The knives 20 and 2| are so positionedwith respect to the coiled coil portion of the filament as to leave onthat end a straight leg 168mils in length, the equivv the resistancecoil24 of'the furnace 25. The coil" ale'nt of the straight leg at the otherend of said 3 0mm. The legs are both parallel to the lonkitudiual axisofthe filament and can now be bent to som -ether'ah'g eurdesired. Thetemporary 1 mandrel l5 iS-theh moved to the leftto withdraw it from thefilament and jaw 1'6 whereupon the jaws I6 and I! are separated, therebyfreeing the filament 22 and allowing-it to drop out of posi-- tion. Anew filament is started by movement of jaws l6 and I1 toward the spindlel8 which places the newend of the mandrel and filament wire assembly l2between the said jaws l6 and I1. 'Ihe'mandrel I5 is also moved to theright and ,enters the aperture in the spindle l8 berore' the coilingoperation begins. The filaments released-from themachlne are veryuniform in length, have equal straight legs at both ends parallel tothe" axis of the coiled coil portion and have expanded so that thelatter coils now have a pitch of 69 turns per inch. The unwinding of thelatter coils is not of serious consequence as it has occurred evenlyfrom end to end. when the final, or temporary mandrel in this case, is

not removed, as in the conventional'method of operation, only'the endportions unwind and the coils are set in this position in the heattreatment. The unwindingof the filament wire on the fixed mandrel isnegligible since it effects" such a very small "portion of the totalamount of filament wire.

Thefilaments 22 are heat-treated again, this time to set the coiled coilor triple'colled'portion, as the case may be, and toremove furtherstrains.

The "treatment, as shown -in Fig.-6, preferably Wakes place in'apparatus-whlchtreats said filaments individually and which isthesubject mato! myco-pending application Serial 'No. 133,854. filed'March30,1937. In this'apparatus the filaments are placed in a tungsten boat23 of exceedingly small mass and are inserted in "24 in this instance isheated to 2000-2 200 C. by the passage of electricity therethrough andheats the filament 22 and. boat 23 which areeremoved therefrom after 5seconds. Tungsten-is the ma terialpreierred for'the boat since it cannot-con-.

taminate the filament and withstand the high 1 temperatures. ofthetreatment. A steady ofa non-oxidizing gas, in this case substantiallydry hydrogen, is introduced into the furnace 25 through the pipe 26 toprevent oxidation of the filament 22, the resistance coil 24, the boat23 and other parts heated by the 5811110011 24/ It' presumed that a.portion of the total time of the treatment is taken to bringthe filament22 tothe maximum temperature thereof because of the -small mass of theboat 23 and its proximity to the heating coil 24. Upon being withdrawnfrom the resistance coil 24,'one second is allowed for the filament 22to-cool whereupon it is removed from the .furnace 25.

With difierent sizes and kinds of filament wire it is desirable tochange the treatment accordingly and generally a treatment for betweenthree and five seconds in a furnace at a temperature between 1900-and2300 C. is sufilcient for most filaments of the smaller conventionalsizes. The temperature of the treatment is selected from the behavior ofthe. filament which becomes brittle if too high a temperature is usedand is not sumciently relieved'of its strains if the temperature istoo'low. The optimum temperature is a compromise and is considered to bethat which pro duces the most satisfactory filament both for performanceand for commercial lamp production 'resistance coilf-i s betw n u Iflar'ger a ran e-swe ters alifl am n r treated slightly'higherteniperatures are often much as 30 seconds? methods. The temperaturesindicated were measured by an optical pyrometer sighted through a windowin"the furnace wall and onto the resistance coil 24 and have been foundto be about 225 C:"high(=.r than that reached by the boat 23 and thefilament 22 and the truest ob- .tainable. In measuring the temperatureor the resistance coil 24, the readings are corregted for thetransmission factor or the window; .Diihculty is experienced in, making(absolute. 'teniperature measurements becauseipf the 'highemissivity ofthe tungsten coil 2'4"; tungsten boat '23 iand' -filament assembly 12which leads "to'consider'able error in apparent temperature readings.comparison to black body conditions. Thej225 difterence in temperaturebetween the'resistance .coil 24 and the filament 22-was foundbyexperipears'that m sojwattinlam assemhlyjlsonly heated to btw' a, 72* Wand 2200'- c.

required and fine s? 11 ea ened na The wattage 'ofel'erificoiwdiiiedby'tnefresistance coil is. usedto indicatef'thetemperature of the treatment afterjthe -'lnitial"temperaturereadings aretaken." tieatment the filament 22 contractsslightlyso that theme] coilsare now at substantially 69% turns per inch.

This change in filamentlehgth hasfbeen round to vary considerablyg'inthe acceptable range of v the heat treatment anditIhasjbeenIoiindpossible to alter the len'gt'hlofthegfilament somewhatby changingtne"--temperature'- ot jflie' treatment.

Higher temperaturescause aigreater increase in the length of thefilament.

The fixed mandrel"! r'both fixed mandrels as :the case may be, arenowaremoved whereupon the filament 22 is mounted on the inner structureof the lamp. The mandrel liispreferably removed chemically by dissolvingit in acid whereupon the filament 22 is rinsed and dried in the usualway. During this operation the filament contracts until the pitch is 70tumsper inch which shows that not all of the strains are removed in theparticular instance by the heat treatments. Photomicrographs of thefilament at this point show that very little if any change has'occurredin the wire during heat treatment [since it is still fibrous. Thestructure of the molybdenum mandrel on the other hand is no longerfibrous but indicates considerable development of grain size approachingthat of single crystals.

The filaments 22 being either of coiled coil or triple coiledconstruction are very concentrated and, being treated according to mymethod, are simply mounted on the lead-in wires 21 and 28 of the lampshown in Fig. 7 and are preferably engaged by one intermediate support29. The straight singly coiled legs of the filament 22 are clamped inhooks at the ends of the leading-in wires 21 and 28 which are designedto hold said filament 22 when cold under slight tension to oi the lamp,but I havefo'uhd that once d i afi s t mblie t' 's ond temporarymandreh' temporary -maridrel before! further. ent and ,lmmedlately timeto remove therein res ti 'g as; the second coiling-operalion and to setthe filament; and removingthe v .sdrawing: the second. temporary mandrelbefore chiefly by the coiling operation; repeatedlyicoil- 4 facilitateuniform mounting. Aiter mou nting. the filament 22 is found to have 69turns pefr inch in the final coils.

The lamp is nowcompletely assembled whereupon the filament 22'ispermanently set and whatever getter is introduced the'reonis driven atnormal and. abnor- J chiefly bythecoiling operation; forming from saidmandrel-andfilament assembly a plurality oi individualcoiled filamentswith straight end portions by winding theintermediate portion around asecond temporarymandrel and severing theone end-portionfl from v theremainder of said off byoperating' the lamp v assembly, i x nmediatelywithdrawing saidsecond malvoltages. ior' very short lntervals oi time..,temporary ma nd relbefore juriher heattreat- During. this process thefilament a 'ain changesl ';ment; .heat treating the-filaments to removea shape slightly'and in quantity production the secconsiderable amountoi the-strains produced by nd coiling is found to have apitch'of between581 --i;h esecond coiling andto-set the filaments; and and 62 turns perinch. Th s r 'i e ofdlfierence 3 removingth first -mandr el -from;saidfilaments. is acceptable o m rcial lamp production 5. Inc processofmalrlng multiple colltungsten since the changes in thefilaments are moregenfilaments.,which consists in winding a filament eral thanbeiore. andare consequently of much wire arounda mandrelpheat treating-the manlessimportance. Obviously there. is. no means drel and the filamentwire-assembly to remove a for calculating the amount of change whichtakes considerable part of: the .strains= therein producted-chiefly bythe calling operation; coilingthe place in the filament 22 duringthemanufacture the -demandrel andgthe filament wire assembly. about s'iredfinal conditions .are reached by trial, my a second temporary mandreland immediately process assures that these same resultsjaresewithdrawing thesecond temporary mandrel becured regularly within apractical range. I tore-further heat treatment; heating the first What Iclaim as new and desireiJto secure by mandrel --and.the; filament ,wireassembly to a Letters Patent of the United 'Statesis'; 3temperature-Miapproximately 1675 to 2075'. C. --,ior iromthree to five'secondsin a non-oxidizing ;atmosphere.=- to.=remove a considerableportion of 1. The processf oi nialsing multiple ,'cc il 1 'filameatswhich consists in windings. filament wire. arou en eli, heat eat se tmaqd and the filam "t wire hsemhly to} siderableQ p .-6 .-;Ci-he processof making 1 mean gless chiefly by the .cblllihg' operatioh; coilinglthemanamiable-a tun sten withdrawing ,the second v 'heat' -tjreatingthe first mandrel andthe' filament wirea'ssembly a second a considerable.p'art of the strains .wirmaroundia zmandrelza heat treating the manzdrelfand the-filament wire assembly to remove a considerable partofthe3strains therein produced chiefly-byrthe-coiling operation; coilingthe man- 10nd temporary -mandre1:-and immediately withfirst mandreliromthe filament coil. e 2. The process of making multiple .coil fila-.iurther heat treatment: heating the first m'anments which consists inwind ng a fil men Wire dreland the filament wire assembly .toa.temaround a ma r t e sit e ma d e perature;of approximately11775 to 1975c. for d he filament W assembly i i fw h onabout five seconds in:anon-oxidizing atmosphere siderable partof the strains therein producedto remoye-a-considerable portion of the strains thereinresulting-iromthe second coiling operation andto set .the filament; and removing thefirst mandrel irom the'filament coil.

- 7. The process oi making multiple coil tungsten filaments whichconsists inwmding a filament ing a portion of the mandrel and the.filament wire assembly about a second temporary mandrel, severing it toform individual coiledcoil filaments, and immediately withdrawing thesec- 0nd temporary mandrel before further heat treatment; then heattreating said filaments to set them and finally removing the firstmandrel from the said individual filaments.

3. The process of making multiple coil filaments which consists inwinding a filament wire around a mandrel; heat treating the mandrel andthe filament wire assembly to remove a considerable part of the strainstherein produced chiefly by the coiling operation; repeatedly coiling aportion of the mandrel and the filament wire assembly about a secondtemporary mandrel, severing it to form individual coiled coil filamentsand immediately withdrawing the second temremove. a considerable portionof the strains porary mandrel before further heat treatment; thereinproduced by the second coiling operation heat treating each of the saidindividual filaand to set the filament; and removing the-first mentsseparately to remove a considerable part mandrel from the filament coil.of the strains therein resulting from the second coiling operation andto'set the filaments; and removing the first mandrel from the saidindividual filaments. I

4. The process of making multiplecoil filaments which consists inwinding 9. fllamentwire around a mandrel; heat treating the mandrel andthe filament wire assembly to remove a considerable part oi. the strainstherein produced and the filament wire assembly to approximately 1500 toi700 C., for about sixteen seconds in a non-oxidizing atmosphere toremove a considerable part of the strainstherein produced chiefly andthe-filament wire assembly about a second temporary mandrel andimmediately withdrawing the second temporary mandrel before further heattreatment; heating the first mandrel and the filament wire assembly to atemperature of approximately 1675 to 2075 C. for from three to fiveseconds-in a non-oxidizing atmosphere to filaments which consists inwinding a filament wireabout a mandrel; heating the mandrel and thefilament 'wire' a'ssembly to approximately 1500 to 170Q'. C. .for aboutsixteen'seconds in a nonoxidizing atmosphere to remove a considerablepart of the strains therein produced by the coiling operation;repeatedly coiling a portion of the mandrel and the filament wireassembly ab ut the strains therein resulting from the.secondfilamentsawhichziconsistsin; .winding -afilament drel andthefilamentwire' assembly about a sec wire around a mandrel; heating themandrel by the coiling operation; coiling the mandrel 5 8. Theproeess ofmaking multiple coil tungsten a second temporary mandrel, severing it toform individual coiled-coil filaments and immediately withdrawing thesecond temporary mandrel before further heat treatment; heating theindividual coiled coil filaments to approximately 1775 to 1975 C. forabout five seconds in a non-oxidizing atmosphere to remove aconsiderable portion of the strains therein resulting from the secondcoiling operation and to set the filaments; and removing the firstmandrel from the fi1a ments.

9. The process of making multiple coil tungsten filaments which consistsin winding a filament wire about a mandrel; winding the mandrel and thefilament assembly about a second mandrel; heating the mandrel and thefilament wire assembly to approximately 1500 to 1700 C. for

about sixteen seconds in a non-oxidizing atmosphere to remove aconsiderable part ofthe strains therein produced chiefly by thecoilingwoperation; repeatedly coiling the mandrel and the filament wireassembly about a third temporary mandrel, severing it to form individualtriple coiled filaments, and immediately withdrawing the third.temporary mandrel before further heat treat-- ment, heating the triplecoiled filament assembly to approximately 1775 to 1975 C. for about fiveseconds in a non-oxidizing atmosphere to remove a considerable portionof the strains therein produced by the third coiling operation and toset the filament; and removing the first and second mandrels from saidfilaments.

WILLIAM P. ZABEL.

CERTIFICATE OF CORRECTION.

Patent No. 2, lh2,8 65.

January 3, 1959.

WILLIAM P, ZABEL. It is hereby certified that error appears in theprinted specification of the above numbered patent requiring correctionas follows: column, line 52, claim 1, after "mandrel" sert instead thewords and immediately; line 5h, "and immediately" and insert insteadasemicolon; ters Patent should be read with this correction therein thatPage h, first strike out the semicolon and insame claim, strike out andthat the said Letthe same may conform to the record of the case in thePatent Office.

Signed and sealed this 21st day of February, A. D. 1939.

(Seal) Henry Van Arsdale. Acting Commissioner of Patents.

